Wiktionary
n. (context mineral English) The iron-rich endmember of the pyroxene group having a monoclinic crystal system.
Wikipedia
Hedenbergite, Ca Fe Si O, is the iron rich end member of the pyroxene group having a monoclinic crystal system. The mineral is extremely rarely found as a pure substance, and usually has to be synthesized in a lab. It was named in 1819 after M.A. Ludwig Hedenberg, who was the first to define hedenbergite as a mineral. Contact metamorphic rocks high in iron are the primary geologic setting for hedenbergite. This mineral is unique because it can be found in chondrites and skarns ( calc–silicate metamorphic rocks). Since it is a member of the pyroxene family, there is a great deal of interest in its importance to general geologic processes.